Make tests work on latest Chrome browsers.
Make tests work on latest Chrome browsers.

Chrome now returns RGB values rather than hex when it's asked to find CSS
properties. Amend tests to allow either RGB or hex, so tests still pass in
all browsers.

alphagov/spotlight,tijmenb/spotlight,tijmenb/spotlight,alphagov/spotlight,keithiopia/spotlight,tijmenb/spotlight,alphagov/spotlight,keithiopia/spotlight,keithiopia/spotlight